In laptop computers and other electronics devices, hot components near the inner case wall of the electronics device often create external hotspots that can be uncomfortable or dangerous to the user. In other words, when an electrical component is being used, the electrical component may generate heat. This electrical component may transfer heat to the enclosure of the device, which essentially creates a hotspot on the enclosure that may be uncomfortable or dangerous to the user especially in the case of a metal enclosure.
The International Electrotechnical Commission (IEC) provides a set of standards for electrical devices, which includes a maximum temperature limit for areas on the outside of the device itself. Typically, most electronic manufacturers adhere to this requirement by limiting the temperature below the maximum temperature provided by the IEC. One particular example of an IEC standard indicates that if the device has a metal or otherwise thermally-conductive surface, the surface must be held at a lower temperature than an equivalent plastic surface. For example, with heated metal surfaces, the heat can be transferred quickly to the user touching the hot metal surface. Therefore, the metal surface can feel relatively hot even at a relatively low temperature. However, metal surfaces for electrical devices are typically used because they can quickly transfer heat from the hot electrical component, thereby keeping the hot electrical component cooler. As such, in some situations, a hotspot on the metal enclosure may occur over the hot electrical component. Further, in the event that an electrical component (e.g., CPU) is processing video graphics, the metal case enclosure may become very hot in the area of the electrical component. Surfaces composed of, for example, plastic, glass, ceramic, and wood, also can develop hotspots in the same or similar ways.
To avoid a hot spot on the case enclosure, a system designer may create an air gap between the hot component and the enclosure. The size of the air gap may be relatively proportional to the usefulness of the insulation, e.g., the larger the air gap between the hot component and the enclosure, the better the thermal insulation. As such, the size of the air gap may be considered a critical item for determining the overall thickness of the device. However, in the area of consumer electronics, thinner electronic devices may be more marketable, while bulkier consumer electronics may have a perception of being of lower quality. Therefore, there may be an incentive to design an electronic device as thin as possible, which greatly affects the air gap, thereby affecting the heat transferred to the user.
In many consumer electronics devices, the heat-generating components are located on a main logic board (MLB), and the MLB is attached to the case enclosure with adhesive material. Because the MLB touches the housing through the adhesive, the adhesive conducts heat away from the MLB to the housing. Even when the MLB is separated from the case enclosure by small area standoffs or pillars (e.g., located at the corners of the MLB) to create an air gap between the MLB and the case enclosure, heat still is conducted through the standoffs and the adhesive that connects the standoffs to the case enclosure. When the thermal conductivity of the standoffs and the adhesive is greater than the thermal conductivity of air, as is generally the case, the standoffs and the adhesive create a thermal short-circuit between the MLB and the case enclosure, such that the usefulness of the air gap between the MLB and the case enclosure is limited.